title: Long-term stability of thermophilic co-digestion submerged anaerobic membrane reactor encountering high organic loading rate, persistent propionate and detectable hydrogen in biogas.
abstract: The performance of thermophilic anaerobic co-digestion of coffee grounds and sludge using membrane reactor was investigated for 148 days, out of a total research duration of 263 days. The OLR was increased from 2.2 to 33.7 kg-COD/m(3)d and HRT was shortened from 70 to 7 days. A significant irreversible drop in pH confirmed the overload of reactor. Under a moderately high OLR of 23.6 kg-COD/m(3)d, and with HRT and influent total solids of 10 days and 150 g/L, respectively, the COD removal efficiency was 44.5%. Hydrogen in biogas was around 100-200 ppm, which resulted in the persistent propionate of 1.0-3.2g/L. The VFA consumed approximately 60% of the total alkalinity. NH4HCO3 was supplemented to maintain alkalinity. The stability of system relied on pH management under steady state. The 16SrDNA results showed that hydrogen-utilizing methanogens dominates the archaeal community. The propionate-oxidizing bacteria in bacterial community was insufficient.
authors.affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum, PR China; Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Japan. Electronic address: qiaowei@cup.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Qiao
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Takayanagi
authors.forename: Qigui
authors.initials: Q
authors.lastname: Niu
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shofie
authors.forename: Yu You
authors.initials: YY
authors.lastname: Li
mesh_terms: D000468:Alkalies / Q000032:analysis; D000641:Ammonia / Q000032:analysis; D000693:Anaerobiosis; D001105:Archaea / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism; D001639:Bicarbonates / Q000032:analysis; D001673:Biodegradation, Environmental; D056804:Biofuels / Q000032:analysis*; D019149:Bioreactors / Q000382:microbiology*; D001709:Biotechnology / Q000379:methods*; D002021:Buffers; D005232:Fatty Acids, Volatile / Q000032:analysis; D006859:Hydrogen / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008567:Membranes, Artificial; D009930:Organic Chemicals / Q000032:analysis*; D010802:Phylogeny; D011422:Propionates / Q000032:analysis*; D012722:Sewage / Q000382:microbiology; D013696:Temperature; D013997:Time Factors
chemical_list: D000468:Alkalies; D001639:Bicarbonates; D056804:Biofuels; D002021:Buffers; D005232:Fatty Acids, Volatile; D008567:Membranes, Artificial; D009930:Organic Chemicals; D011422:Propionates; D012722:Sewage; D000641:Ammonia; D006859:Hydrogen
keywords: Anaerobic co-digestion; Long-term stability; Membrane reactor; Organic loading rate; Thermophilic